Service Manual

Step Task Command Command Mode
Range: 0-3. Separate queue values with a comma;
specify a priority range with a dash; for example: pfc no-
drop queues 1,3 or pfc no-drop queues 2-3 Default: No
lossless queues are congured.
Data Center Bridging: Default Conguration
Before you congure PFC and ETS on a switch see the priority group setting taken into account the following default settings:
DCB is enabled.
PFC and ETS are globally enabled by default.
The default dot1p priority-queue assignments are applied as follows:
Dell(conf)#do show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 2 0 1 3 4 5 6 7
Dell(conf)#
NOTE: In Egress queue assignment (8 queues in S6000 and Z9500, 4 against in S5000 and S4810.
PFC is not applied on specic dot1p priorities.
ETS: Equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.
To congure PFC and ETS parameters on an S6000 interface, you must specify the PFC mode, the ETS bandwidth allocation for a
priority group, and the 802.1p priority-to-priority group mapping in a DCB map. No default PFC and ETS settings are applied to
Ethernet interfaces.
Conguring PFC and ETS in a DCB Map
switch supports the use of a DCB map in which you congure priority-based ow control (PFC) and enhanced transmission
selection (ETS) settings. To congure PFC and ETS parameters, you must apply a DCB map on interface. This functionality is
supported on the platform.
PFC Conguration Notes
PFC provides ow control based on the 802.1p priorities in a converged Ethernet trac that is received on an interface and is
enabled by default when you enable DCB. As an enhancement to the existing Ethernet pause functionality, PFC stops trac
transmission for specied priorities (CoS values) without impacting other priority classes. Dierent trac types are assigned to
dierent priority classes.
When trac congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of the trac that needs to
be stopped. DCBx provides the link-level exchange of PFC parameters between peer devices. PFC allows network administrators to
create zero-loss links for SAN trac that requires no-drop service, while at the same time retaining packet-drop congestion
management for LAN trac.
On switch, PFC is enabled by default on Ethernet ports (pfc mode on command). You can congure PFC parameters using a
DCB map or the pfc priority command in Interface conguration mode. For more information, see Conguring Priority-Based
Flow Control.
As soon as you apply a DCB map with PFC enabled on an interface, DCBx starts exchanging information with a peer. The
IEEE802.1Qbb, CEE and CIN versions of PFC TLV are supported. DCBx also validates PFC congurations that are received in TLVs
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Data Center Bridging (DCB)